Fig 4Difference Engine No. 2 · 3DDrag to orbit · drag the crank · ← → · Space · In = 0 · f = 0 · Δ1 1 · turn 1 of 4: odd → even · 1 row printed
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The wheels being turned: a receiving column counting up while its giver counts down, or the one wheel taking a carryFigure wheels, 8 columns × 31, the digits 0–9 engraved round each drum; a tab at 9 → 0 warns the carry lever behindSector gears between the columns; a column rises or drops into mesh, so one sector column serves each additionThe printer: copy sectors and racks take column f off in turn 3 to a row of 31 type wheels; the platen prints the checking copy on the paper web, the anvil impresses the stereotype trayPaletteThe same engine as Fig 4's SVG pages, seen in 3D. Every solid here is generated from the one layout (parts.mjs) and the one model (engine.mjs) the SVG figure is drawn from: the frame's slabs, turned parts, ring bands and prisms are the very shapes the SVG build records for its audit, the 248 figure wheels, 217 sector gears, 248 carry levers, 7 helical carry sweeps, 31 copy sectors and wheels, 31 racks, 31 type spindles and 31 type wheels are instanced from the same builders and placed by the same formulas, and every frame poses them from poseAt(θ), as the SVG does; the readout, the setting panel and the checking copy are the SVG page's own. It opens in the SVG's true isometric view (orthographic, azimuth 68°, elevation 36°, the whole machine framed as on the SVG card) and can be orbited: drag to turn, wheel or pinch to zoom, I or the button to snap back; left alone it revolves slowly. What differs: faces are shaded by the kit's four-tone rule from one light, outlines are the solids' edges (creases over 20°) and silhouettes rather than the painter's hand-ordered strokes, the digit rims and the printed and impressed rows are canvas textures, there is no glow halo (glow mode only lights the working parts amber), the copy wheels, the main gear and the crank pinion turn with what drives them (the spindle pinions stand still), and the type rims carry the ten digits at 9° a face so that the digit set is the one on top, behind and below. The crank, cams and main shaft turn together as the SVG draws them. Light, dark and City palettes are the figure's own tokens.